I am currently trying to use the Triple-Speed Ethernet core in my Nios2 project to send a raw Ethernet frame from my DE2-115 FPGA board to the PC and capture it with Wireshark. I used the "Using Triple-Speed Ethernet on DE2-115 Boards" pdf as a reference. The frame is sent, but it seems to be encapsuled in a TCP/IP packet from with IP src and IP dest 127.0.0.1. Also, every fifth byte of the data that is captured is 0x01, which makes me think there is also some clocking problem going on. It does not matter if the packet is sent via a point-to-point connection or over the router, it looks the same either way. I know that the Ethernet core does not implement a TCP/IP stack by default, so I assume that the network controller on my PC encapsules the packet this way, but I am not sure why. Is anything wrong with my code?
My top.vhd: https://pastebin.com/wNk0bpEp
My main.c: https://pastebin.com/yDkGres3
Please tell me if more information is needed. I would be very happy if someone could point me in the right direction here.